net: airoha: Add the capability to allocate hwfd buffers via reserved-memory

net: airoha: Add the capability to allocate hwfd buffers via reserved-memory

In some configurations QDMA blocks require a contiguous block of
system memory for hwfd buffers queue. Introduce the capability to allocate
hw buffers forwarding queue via the reserved-memory DTS property instead of
running dmam_alloc_coherent().

Signed-off-by: Lorenzo Bianconi <lorenzo@kernel.org>
Reviewed-by: Simon Horman <horms@kernel.org>
Link: https://patch.msgid.link/20250521-airopha-desc-sram-v3-3-a6e9b085b4f0@kernel.org
Signed-off-by: Paolo Abeni <pabeni@redhat.com>